This invention relates to the field of radio transport of alphanumeric messages to and from handheld terminal units, mobile units and fixed installations, and specifically to a method and means for coordinating the transmission of return acknowledgement messages in a transmission scheme wherein certain messages require a return acknowledgement message. The present application is related to the instant assignee's U.S. Pat. No. 4,481,670 issued Nov. 6, 1984, entitled "Method and Apparatus for Dynamically Selecting Transmitters for Communications Between a Primary Station and Remote Stations of a Data Communications System" and invented by Thomas A. Freeburg, U.S. patent application Ser. No. 603,399 filed Apr. 24, 1984 entitled "Data Communications System Transmitter Selection Method and Apparatus" and invented by Stuart W. Thro, and Ser. No. 627,270 filed July 2, 1984 entitled "Self-Calibrating Signal Strength Detector", also invented by Stuart M. Thro.